fix: trigger sign_checker on Projects-info and networks metadata changes

[Copilot]

sign_checker workflow only fired on assets/** changes, silently skipping signature verification for owner (Projects-info/**) and network parachain (networks/**) metadata PRs.

Changes

• Added Projects-info/** and networks/** to paths: in .github/workflows/sign_checker.yaml

paths:
  - Projects-info/**
  - networks/**
  - assets/**

Checklist

• Use the owner account that submitted registrar_reserve to sign the project information, and fill in the signature.
• After each update of the project information, please sign the latest data and submit the signature.
• Add a description for your pr, the description includes the original data.
• Fill up the signature of the original data, signature account to Signature Auto check.

Signature Auto check

Para ID Owner & Signature Account:
<REPLACE THE OWNER>

Data that needs to be signed:
file

Signature Hash: <REPLACE THE SIGNATURE>